Currently, radio communication technologies for providing various multi media services in a radio communication environment have been developed. A high transmission rate is required to provide multi media services having a relatively high quality. Thus, various studies for supporting the high transmission rate have been recently made. Of theses, a study for a Multiple Input Multiple Output (MIMO) technology has been actively made.
The MIMO technology may increase a channel capacity within limited frequency resources by using multiple antennas. The MIMO technology may use multiple antennas in the case of a superior scattering environment, and thus providing a channel capacity in proportion to a number of antennas, in theory.
However, in the MIMO technology, a space and area in which antennas are able to be installed may be limited, and intervals between the antennas may adversely affect a communication performance. Specifically, radio channels may have a higher correlation therebetween along with a reduction in the interval between the antennas. In particular, the radio channels have a significantly high correlation therebetween in the case of antennas having an identical polarization. Interference generated between the radio channels may decrease reliability of data communication, and also decrease the transmission rate.
The MIMO technology is required to perform an operation for coding data in advance for the purpose of effective transmission of data, which refers to precoding. Also, a scheme in which a rule for preceding data is expressed as a matrix refers to as a preceding matrix, and further a set of the preceding matrixes refers to as a codebook.
A base station may precode data based on information about a channel state from the base station to a mobile station, and transmit the precoded data to the mobile station. The mobile station may estimate the channel state from the base station to the mobile station, and feed back information about the estimated channel state to the base station. In order to increase a preceding performance, the mobile station is required to transmit more accurate information about the channel state, however, a data transmission capacity from the mobile station to the base station is limited, which results in causing difficulties in transmission of accurate information.